Photosensitive resin composition, photosensitive element, production method of resist pattern and production method for printed circuit board

ABSTRACT

A photosensitive resin composition is here disclosed which satisfies the following (1) and (2):  
     (1) when a 1.0 wt % aqueous sodium carbonate solution is sprayed by a spray on a layer of the photosensitive resin composition having a thickness of 37 to 42 μm under the following conditions, the photosensitive resin composition layer being able to be removed within 20 seconds, the above conditions being that an internal diameter of a nozzle of the spray is 1.2 mm, a spraying pressure is 0.05 MPa, and a distance between a point of the spray nozzle which is closest to the photosensitive resin composition layer and the photosensitive resin composition layer is 50 mm; and  
     (2) when the 1.0 wt % aqueous sodium carbonate solution is sprayed three times for 36 seconds under the above conditions on a cured film obtained by laminating a layer of the photosensitive resin composition having the above thickness on a copper-clad laminate having 18 three-continuous holes in which 3 holes each having a diameter of 6 mm are continuously integrated and which has a length of 16 mm, and then photo-curing the layer with an exposure capable of curing 24 steps in a 41-step tablet, the number of holes where the cured film is broken being 5 or less.

TECHNICAL FIELD

[0001] The present invention relates to a photosensitive resincomposition, a photosensitive element, a production method of a resistpattern, and a production method of a printed wiring board.

BACKGROUND ART

[0002] Methods for producing a printed wiring board are classified intotwo a tenting method and a plating method. In the tenting method, copperthrough holes for mounting a chip are protected by use of a resist,followed by etching and stripping of the resist, so as to form a circuitboard. Meanwhile, in the plating method, copper is deposited in throughholes by electroplating, and the through holes are then protected bysolder plating, followed by stripping of a resist and etching, so as toform a circuit board.

[0003] In these methods, a photosensitive resin composition and aphotosensitive element are used as the resist, and in particular, fromthe viewpoint of running costs and a working environment, an alkalidevelopable resist is primarily used. Then, after the resist is cured,uncured portions are removed by an alkali developer, followed by rinsingby means of a spray pressure. Thus, a photosensitive resin compositionto be used is required to have a tenting property which makes thecomposition unbreakable against the developer and the spray pressureused for rinsing, i.e., tent reliability. Further, in the plating methodin particular, since a current density in a finely lined portion on aprinted wiring board is higher than a current density in a loosely wiredportion, plating in the finely lined portion becomes thicker than theresist, so that the resist in the portion is apt to be resist residue(resist residue due to overhanging). Hence, it is necessary that theresist does not remain after stripping even if the plating is overhung,that is, it have excellent stripping property.

[0004] In response to such requests, a photosensitive resin compositionusing a vinyl urethane compound and having good tent reliability isdisclosed in Japanese Patent Application Laid-Open No. 271129/1993.However, such a photosensitive resin composition tends to havedifficulty in conforming to increases in resolution which has beenincreasingly demanded year by year along with increases in density andprecision of wiring of a printed wiring board. It is assumed that thisis ascribable to a fact that an isocyanate residue having an urethanebond does not have excellent developability.

[0005] Further, an acrylate compound in which a polyethylene glycolchain solely exists is disclosed in Japanese Patent ApplicationLaid-Open No. 232699/1993. However, when the polyethylene glycol chainexists alone, hydrophilicity is so strong that such problems as thedeterioration of tent reliability or stripping property occur.Meanwhile, an acrylate compound in which a polypropylene glycol chainexists alone exhibits low resolution. Further, such an acrylate compoundcan be easily removed by an alkali developer. Hence, it causes theoccurrence of sludge which is insoluble in the developer, and the sludgecauses a short or a break when adhered to a substrate.

[0006] In addition to the foregoing requirements with respect to tentreliability and stripping property, it has also been necessary toshorten developing time for the purpose of improving the produceabilltyof a printed wiring board. The present inventors have studied reductionin developing time in order to make a production process short.Heretofore, when a photosensitive resin composition layer having athickness of about 37 to 42 μm is developed, development requires atleast 25 seconds. However, if the developing time can be reduced to 20seconds or less, the developing time is significantly reduced, andproduction time is in turn reduced. To reduce developing time, it iseffective to improve the hydrophilicity of a binder polymer of thephotosensitive resin composition However, an improvement in thehydrophilicity of the photosensitive resin composition lowers resistanceto the developer, so that breakages of tents are liable to increase, inother words, tent reliability is liable to be lowered. For this reason,a photosensitive resin composition which achieves a reduction indeveloping time and has fully satisfactory tent reliability hasheretofore not been available.

DISCLOSURE OF THE INVENTION

[0007] An object of the present invention is to provide a photosensitiveresin composition which can shorten developing time and has highstripping property and tent reliability.

[0008] The present invention is a photosensitive resin composition whichsatisfies the following (1) and (2). (1) When a 1.0 wt % aqueous sodiumcarbonate solution is sprayed on a layer of the above photosensitiveresin composition having a thickness of 37 to 42 μm under the followingconditions, the photosensitive resin composition layer can be removedwithin 20 seconds. The above conditions are that an internal diameter ofa spray nozzle is 1.2 mm, a spraying pressure is 0.05 MPa, and adistance between a point of the spray nozzle which is closest to thephotosensitive resin composition layer and the photosensitive resincomposition layer is 50 mm. (2) When a 1.0 wt % aqueous sodium carbonatesolution is sprayed three times for 36 seconds (36 seconds per time)under the foregoing conditions on a cured film obtained by laminating alayer of the photosensitive resin composition having the foregoingthickness on a copper-clad laminate having 18 three-continuous holes inwhich 3 holes each having a diameter of 6 mm are continuously integratedand which has a length of 16 mm, and then photo-curing the layer with anexposure capable of curing 24 steps in a 41-step tablet, the number ofholes at which the layer is broken is 5 or less.

[0009] Further, the layer of the photosensitive resin composition of thepresent invention can be removed preferably within 19 seconds, and morepreferably within 18 seconds.

[0010] Further, the present invention is a photosensitive resincomposition comprising (A) a binder polymer, (B) a photopolymerizablecompound and (C) a photopolymerization initiator, wherein the component(B) contains polyalkylene glycol di(meth)acrylate having both anethylene glycol chain and a propylene glycol chain in its molecule, andthe component (C) contains acridine or an acridine-based compound havingat least one acridinyl group in its molecule.

[0011] Further, in the photosensitive resin composition of the presentinvention, the component (C) includes a acridine-based compound havingat least one acridinyl group in its molecule represented by a generalformula (II):

[0012] (where R³ represents an alkylene group having 6 to 12 carbonatoms).

[0013] Further, the present invention is a photosensitive resincomposition comprising (A) a binder polymer, (B) a photopolymerizablecompound and (C) a photopolymerization initiator, wherein the component(A) is a polymer component having a weight average molecular weight of30,000 to 70,000, and the component (B) includes a photopolymerizablecompound which has at least one ethylenically unsaturated bond in itsmolecule and which has 15 or more alkylene glycol units each having 2 to6 carbon atoms.

[0014] Further, the present invention is a photosensitive resincomposition comprising (A) a binder polymer, (B) a photopolymerizablecompound and (C) a photopolymerization initiator, wherein the component(A) is a polymer component having a weight average molecular weight of30,000 to 70,000, and the component (B) includes a photopolymerizablecompound which has at least one ethylenically unsaturated bond in itsmolecule and a molecular weight of not lower than 900.

[0015] Further, the present invention is a photosensitive resincomposition comprising (A) a binder polymer, (B) a photopolymerizablecompound and (C) a photopolymerization initiator, wherein based on 100parts by weight of a total of the components (A) and (B), the amount ofthe component (A) is 40 to 80 parts by weight, the amount of thecomponent (B) is 20 to 60 parts by weight, and the amount of thecomponent (C) is 0.01 to 3 parts by weight.

[0016] Further, the present invention is a photosensitive elementprepared by applying any of the above photosensitive resin compositionson a substrate, and drying the applied composition.

[0017] Further, the present invention is a production method of a resistpattern which comprises the steps of: laminating the abovephotosensitive element on a substrate for forming a circuit so that thephotosensitive resin composition layer may come in intimate contact withthe substrate; irradiating it with active light imagewise so as tophoto-cure an exposed potion; and removing an unexposed portion bydevelopment.

[0018] Further, the present invention is a production method of aprinted wiring board which comprises etching or plating a substrate forforming a circuit which has a resist pattern produced thereon by theforegoing resist pattern production method.

[0019] According to the present invention, since high-speed developmentis possible, excellent tent reliability can be attained, and entry of anetching solution, a plating solution or the like into through holes canbe prevented efficiently. As a result, poor conduction, an impropershort and the like in a printed wiring board can be prevented, so that aprinted wiring board can be produced at high yield, consequently, bysignificantly increasing the speed of a production line of printedwiring boards so as to reduce production time, workability andproductivity can be improved.

[0020] Further, according to the present invention, excellent tentreliability, stripping property (overhang stripping property), lightsensitivity, resolution, chemical resistance (plating resistance) andflexibility can be imparted to a photosensitive resin composition.Therefore, the present invention is useful for increasing the densityand resolution of printed wiring.

[0021] Still further, according to the present invention, occurrence ofsludge can be decreased.

[0022] The present disclosure relates to subject matter contained inJapanese Patent Application Nos. 157530/2000 and 395193/2000, thedisclosure of which is expressly incorporated herein by reference in itsentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is an external view of an evaluation substrate used forevaluating an irregularly shaped tent breakage rate in an experimentalexample of the present specification.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] Hereinafter, the present invention will be described in detail.In the present invention, (meth)acrylic acid, refers to acrylic acid andcorresponding methacrylic acid, a (meth)acrylate refers to an acrylateand a corresponding methacrylate, and a (meth)acryloyl group refers toan acryloyl group and a corresponding methacryloyl group.

[0025] A photosensitive resin composition of the present invention is aphotosensitive resin composition which satisfies the following (1) and(2). (1) When a 1.0 wt % aqueous sodium carbonate solution is sprayed ona layer of the above photosensitive resin composition having a thicknessof 37 to 42 μm under the following conditions, the photosensitive resincomposition layer can be removed within 20 seconds. The above conditionsare that an internal diameter of a spray nozzle is 1.2 mm, a sprayingpressure is 0.05 MPa, and a distance between a point of the spray nozzlewhich is closest to the photosensitive resin composition layer and thephotosensitive resin composition layer is 50 mm. (2) When a 1.0 wt %aqueous sodium carbonate solution is sprayed three times for 36 secondsunder the foregoing conditions on a cured film obtained by laminating alayer of the photosensitive resin composition having the foregoingthickness on a copper-clad laminate having 18 three-continuous holes inwhich 3 holes each having a diameter of 6 mm are continuously integratedand which has a length of 16 mm, and then photo-curing the layer with anexposure capable of curing 24 steps in a 41-step tablet, the number ofholes at which the layer is broken is 5 or less.

[0026] The above photosensitive resin composition can be obtained by,for example, containing (A) a binder polymer, (B) polyalkylene glycoldi(meth)acrylate having both an ethylene glycol chain and a propyleneglycol chain in the molecule of a photopolymerizable compound and (C)acridine or an acridine-based compound having at least one acridinylgroup in its molecule.

[0027] Farther, the above photosensitive resin composition can beobtained by, for example, containing (A) a polymer component having aweight average molecular weight of 30,000 to 70,000, (B) aphotopolymerizable compound having at least one ethylenicallyunsaturated bond in its molecule and having 15 or more alkylene glycolunits each having 2 to 6 carbon atoms, and (C) a photopolymerizationinitiator.

[0028] Further, the above photosensitive resin composition can beobtained by, for example, containing (A) a polymer component having aweight average molecular weight of 30,000 to 70,000, (B) aphotopolymerizable compound having at least one ethylenicallyunsaturated bond in its molecule and having a molecular weight of 900 ormore, and (C) a photopolymerization initiator.

[0029] Illustrative examples of the above binder polymer (A) include anacrylic resin, a styrene resin, an epoxy resin, an amide resin, an amideepoxy resin, an alkyd resin, and a phenol resin. From the viewpoint ofalkali developability, the acrylic resin is preferred. These can be usedalone or in combination of two or more.

[0030] The binder polymer (A) used in the present invention can beproduced by radical polymerization of a polymerizable monomer, forexample.

[0031] Illustrative examples of the polymerizable monomer includestyrene, a polymerizable styrene derivative such as vinyltoluene,α-methylstyrene, p-methylstyrene, p-ethylstyrene, p-methoxystyrene,p-ethoxystyrene, p-chlorostyrene or p-bromostyrene, acrylamide,acrylonitrile, a vinyl alcohol ester such as vinyl-n-butyl ether, alkyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dimethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate, glycidyl(meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate,2,2,3,3-tetrafluoropropyl (meth)acrylate, (meth)acrylic acid₆,α-bromo(meth)acrylate, α-chlor(meth)acrylate, β-furyl(meth)acrylate,β-styryl(meth)acrylate, maleic acid, maleic anhydride, a maleicmonoester such as monomethyl maleate, monoethyl maleate or monoisopropylmaleate, fumaric acid, cinnamic acid, α-cyanocinnamic acid, itaconicacid, crotonic acid, and propionic acid.

[0032] Illustrative examples of the above alkyl (meth)acrylate include acompound represented by a general formula (I):

[0033] (wherein R¹ represents a hydrogen atom or a methyl group, and R²represents an alkyl group having 1 to 12 carbon atoms),

[0034] and a compound obtained by substituting the alkyl group of thecompound with a hydroxyl group, an epoxy group, a halogen group or thelike.

[0035] Illustrative examples of the alkyl group having 1 to 12 carbonatoms which as represented by R² in the above general formula (I)include a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, an undecyl group, a dodecyl group, and structuralisomers of these.

[0036] Illustrative examples of the monomer represented by the abovegeneral formula (I) include methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate,hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, and2-ethylhexyl (meth)acrylate. These can be used alone or in combinationof two or more.

[0037] The above binder polymer (A) preferably contains a carboxyl groupfrom the viewpoint of alkali developability and can be produced by, forexample, radical polymerization of a polymerizable monomer having acarboxyl group with other polymerizable monomer. As the abovepolymerizable monomer having a carboxyl group, methacrylic acid ispreferred. Further, from the viewpoint of flexibility, the above binderpolymer (A) preferably contains styrene or a styrene derivative as apolymerizable monomer.

[0038] To improve both adhesion and stripping property, the abovestyrene or styrene derivative is preferably contained as acopolymerization component in an amount of 2 to 30% by weight, morepreferably 2 to 28% by weight, particularly preferably 2 to 27% byweight. When the content is lower than 2% by weight, adhesion is liableto be poor, while when it is higher than 30% by weight, pieces to bestripped become so large that stripping is liable to take long time.

[0039] These binder polymers are used alone or in combination of two ormore. Illustrative examples of binder polymers to be used in combinationof two or more include two or more binder polymers comprising differentcopolymerization components, two or tore binder polymers havingdifferent weight average molecular weights, and two or more binderpolymers having different degrees of dispersion. Further, a polymerhaving multimode molecular weight distribution as disclosed in JapanesePatent Application Laid-Open No. 327137/1999 may also be used.

[0040] The binder polymer preferably has a weight average molecularweight of 30,000 to 70,000, more preferably 35,000 to 65,000,particularly preferably 40,000 to 60,000. When the molecular weight islower than 30,000, film coatability and a tenting property are liable tobe poor. Meanwhile, when the molecular weight is higher than 70,000,developing time is liable to be long. The weight average molecularweight is measured by means of gel permeation chromatography (GPC) andobtained by conversion based on a calibration curve using a standardpolystyrene.

[0041] Further, when two or more binder polymers are used, the weightaverage molecular weight of a polymer component resulting from mixing ofthe binder polymers is measured. For example, the weight averagemolecular weight of a polymer component used in an experimental exampleto be describe later in the present specification and resulting frommixing of a binder polymer having a weight average molecular weight of60,000 and a binder polymer having a weight average molecular weight of30,000 was 55,000.

[0042] As for the degree of dispersion of the binder polymer, the degreeof dispersion (weight average molecular weight/number average molecularweight) of a polymer mixture when two or more binder polymers are usedin admixture or the degree of dispersion of a binder polymer when thepolymer component is used alone is preferably 1.5 to 5.0, morepreferably 18 to 4.0, particularly preferably 2.0 to 3.5. As in the caseof the weight molecular weight, the number average molecular weight isalso measured by GPC and converted by a standard polystyrene.

[0043] The photopolymerizable compound (B) used in the present inventionpreferably has at least one ethylenically unsaturated bond in itsmolecule. However, from the viewpoints of the tenting property andstripping property, the compound (B) contains more preferably two ormore ethylenically unsaturated bonds, particularly preferably twoethylenically unsaturated bonds.

[0044] As the component (B), a photopolymerizable compound having 15 ormore alkylene glycol units each of which has 2 to 6 carbon atoms can beused.

[0045] The number of the carbon atoms is preferably 2 to 6, morepreferably 2 to 5, particularly preferably 2 or 3, from the viewpoint ofthe tenting property. Further, the number of the units, i.e., a totalnumber of recurring units, is preferably 15 to 30, more preferably 15 to25, particularly preferably 15 to 20. When the number of the units issmaller than 15, the tenting property and sensitivity are liable to bepoor, and stripping time is liable to be long. Meanwhile, when thenumber of the units is larger than 30, resolution is liable todeteriorate, and a resist obtained is liable to be brittle.

[0046] The molecular weight of the component (B) is preferably 900 ormore, more preferably 900 to 2,500, particularly preferably 1,000 to1,500. When the molecular weight is lower than 900, the tenting propertyand the sensitivity are liable to be poor, and the stripping time isliable to be long.

[0047] The component (B) preferably contains polyalkylene glycoldi(meth)acrylate having both an ethylene glycol chain and a propyleneglycol chain in its molecule. The (meth)acrylate is not particularlylimited as long as it has both an ethylene glycol chain and a propyleneglycol chain (n-propylene glycol chain or isopropylene glycol chain) asalkylene glycol chains in its molecule. Further, the (meth)acrylate mayalso contain an alkylene glycol chain having about 4 to 6 carbon atoms,such as an n-butylene glycol chain, an isobutylene glycol chain, ann-pentylene glycol chain, a hexylene glycol chain, and structuralisomers of these.

[0048] When a plurality of the above ethylene glycol chains andpropylene glycol chains exist, the ethylene glycol chains and thepropylene glycol chains each do not have to exist continuously and mayexist randomly. Further, primary or secondary carbon in a propylenegroup in the above isopropylene glycol chain may be bonded to an oxygenatom.

[0049] Illustrative examples of an alkylene glycol chain in the moleculeof polyalkylene glycol di(meth)acrylate having at least onepolymerizable, ethylenically unsaturated bond and having both anethylene glycol chain and a propylene glycol chain in its molecule inthe component (B) include a compound represented by a general formula(III):

[0050] (wherein two Rs each independently represent a hydrogen atom oran alkyl group having 1 to 3 carbon atoms, EO represents an ethyleneglycol chain, PO represents a propylene glycol chain, and m¹, m² and n¹are each independently an integer of 1 to 30),

[0051] a compound represented by a general formula (IV):

[0052] (wherein two Rs each independently represent a hydrogen atom oran alkyl group having 1 to 3 carbon atoms, EO represents an ethyleneglycol chain, PO represents a propylene glycol chain, and m³, n² and n³are each independently an integer of 1 to 30),

[0053] and a compound represented by a general formula (V):

[0054] (wherein two Rs each independently represent a hydrogen atom oran alkyl group having 1 to 3 carbon atoms, EO represents an ethyleneglycol chain, PO represents a propylene glycol chain, and m⁴ and n⁴ areeach independently an integer of 1 to 30).

[0055] These are used alone or in a combination of two or more.

[0056] Illustrative examples of the alkyl groups having 1 to 3 carbonatoms in the foregoing general formulae (III), (IV) and (V) include amethyl group, an ethyl group, an n-propyl group and an isopropyl group.

[0057] Total numbers (m¹+m², m³ and m⁴) of repetitions of the ethyleneglycol chains in the above general formulae (III), (IV) and (V) are eachindependently an integer of 1 to 30, preferably an integer of 1 to 10,more preferably an integer of 4 to 9, particularly preferably an integerof 5 to 8. When the number of repetitions exceeds 30, tent reliabilityand the shape of a resist are liable to deteriorate.

[0058] Total numbers (n¹, n²+n³, and n⁴) of repetitions of the propyleneglycol chains in the above general formulae (III), (IV) and (V) are eachindependently an integer of 1 to 30, preferably an integer of 5 to 20,more preferably an integer of 8 to 16, particularly preferably aninteger of 10 to 14. When the number of repetitions exceeds 30,resolution is liable to deteriorate, and sludge is liable to beproduced.

[0059] A specific example of the compound represented by the abovegeneral formula (III) is a vinyl compound (product of Hitachi ChemicalCo., Ltd., trade name: FA-023M) wherein R is a methyl group, m¹+m² is 4(average value), and n¹ is 12 (average value). A specific example of thecompound represented by the above general formula (IV) is a vinylcompound (product of Hitachi Chemical Co., Ltd., trade name: FA-024M)wherein R is a methyl group, m³ is 6 (average value), and n²+n³ is 12(average value). A specific example of the compound represented by theabove general formula (V) is a vinyl compound (product of Shin-NakamuraChemical Co., Ltd, trade name: NK ESTER HEMA-9P) wherein R is a hydrogenatom, m⁴ is 1 (average value), and n⁴ is 9 (average value). There areused alone or in a combination of two or more.

[0060] Further, the component (B) may also contain photopolymerizablecompounds other than the polyalkylene glycol di(meth)acrylate havingboth an ethylene glycol chain and a propylene glycol chain in itsmolecule. Specific examples of such other photopolymerizable compoundsinclude compounds obtained by reacting a polyhydric alcohol with anα,β-unsaturated carboxylic acid, bisphenol-A-based (meth)acrylatecompounds such as 2,2-bis(4-((meth)acryloxypolyethoxy)phenyl)propane,2,2-bis(4-((meth)acryloxypolypropoxy)phenyl)propane,2,2-bis(4-((meth)acryloxypolybutoxy)phenyl)propane and2,2-bis(4-((meth)acryloxypolyethoxypolypropoxy)phenyl)propane, compoundsobtained by reacting a glycidyl-group-containing compound with anα,β-unsaturated carboxylic acid, urethane monomers such as a(meth)acrylate compound having an urethane bond in its molecule,nonylphenoxypolyethyleneoxy acrylate, phthalic-acid-based compounds suchas γ-chloro-β-hydroxypropyl-β′-(meth)acryloyloxyethyl-o-phthalate andβ-hydroxyalkyl-β′-(meth)acryloyloxyalkyl-o-phthalate, and alkyl(meth)acrylate. It is preferred that the bisphenol-A-based(meth)acrylate compound or the (meth)acrylate compound having anurethane bond in its molecule is contained as an essential component.These are used alone or in a combination of two or more.

[0061] As the photopolymerization initiator (C) used in the presentinvention, acridine or an acridine-based compound having at least oneacridinyl group in its molecule is preferably used. Illustrativeexamples of the acridine-based compound include the compoundsrepresented by the above general formula (II), 9-phenylacridine,9-pyridylacridine, 9-pyridylacridine, and bis(9-acridinyl)alkanes suchas 1,2-bis(9-acridinyl)ethane, 1,3-bis(9-acridinyl)propane,1,4-bis(9-acridinyl)butane and 1,5-bis(9-acridinyl)pentane. These areused alone or in a combination of two or more.

[0062] Illustrative examples of the alkylene group having 6 to 12 carbonatoms in the above general formula (II) include a hexylene group, aheptylene group, an octylene group, a nonylene group, a decylene group,an undecylene group, a dodecylene group, and structural isomers ofthese.

[0063] Illustrative examples of the compound represented by the abovegeneral formula (II) include 1,6-bis(9-acridinyl)hexane,1,7-bis(9-acridinyl)heptane, 1,8-bis(9-acridinyl)octane,1,9-bis(9-acridinyl)nonane, 1,10-bis(9-acridinyl)decane,1,11-bis(9-acridinyl)undecane, and 1,12-bis(9-acridinyl)dodecane. Theabove 1,7-bis(9-acridinyl)heptane can be obtained as a product of ASAHIDENKA CO., LTD. with a trade name: N-1717. These can be used alone or ina combination of two or more.

[0064] Further, the photosensitive resin composition of the presentinvention can-also contain photopolymerization initiators other than theabove acridine or acridine-based compound (C) having at least oneacridinyl group in its molecule. Illustrative examples of such otherphotopolymerization initiators include benzophenone,N,N′-tetraalkyl-4,4′-diaminobenzophenone such asN,N′-tetramethyl-4,4′-diaminobenzophenone (Michler's ketone), aromaticketones such as2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propanone-1,quinones such as alkyl anthraquinone, benzoin ether compounds such asbenzoin alkyl ether, benzoin compounds such as benzoin and alkylbenzoin, benzyl derivatives such as benzyl dimethyl ketal,2,4,5-triarylimidazole dimers such as2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer and2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, N-phenylglycine,N-phenylglycine derivative, coumarin compounds, and onium salts. Theseare used alone or in a combination of two or more.

[0065] The above binder polymer (A) is added in an amount of preferably40 to 80 parts by weight, more preferably 45 to 70 parts by weight,based on 100 parts by weight of a total of the components (A) and (B).When the amount is less than 40 parts by weight, a photo-cured productis liable to become brittle and exhibit poor coatability when used as aphotosensitive element, while when it is more than 80 parts by weight,light sensitivity is liable to be unsatisfactory.

[0066] The above photopolymerizable compound (B) is added in an amountof preferably 20 to 60 parts by weight, more preferably 30 to 55 partsby weight, based on 100 parts by weight of the total of the components(A) and (B). When the amount is less than 20 parts by weight, lightsensitivity is liable to be unsatisfactory, while when it is more than60 parts by weight, the photo-cured product is liable to become brittle.

[0067] The proportion of the polyalkylene glycol di(meth)acrylate havingboth an ethylene glycol chain and a propylene glycol chain in itsmolecule, the compound having 15 or more alkylene glycol units eachhaving 2 to 6 carbon atoms or the photopolymerizable compound having amolecular weight of 900 or more in the component (B) is preferably 30%by weight or more, more preferably 40% by weight or more, particularlypreferably 50% by weight or more. When the proportion is lower than 30%by weight, the effect of the present invention is more preferable, andthe proportion is particularly preferably 50% by weight or more. Whenthe proportion is lower than 30% by weight, the effect of the presentinvention is liable not to be obtained.

[0068] The above photopolymerization initiator (C) is added in an amountof preferably 0.01 to 3 parts by weight, more preferably 0.1 to 2 partsby weight, based on 100 parts by weight of the total of the components(A) and (B). When the amount is less than 0.01 parts by weight, lightsensitivity is liable to be unsatisfactory, while when it is more than 3parts by weight, absorption on the surface of the composition increasesupon exposure, so that photo-curing of the inside of the composition isliable to be insufficient.

[0069] The above photosensitive resin composition can contain aphotopolymerizable compound having at least one cationic-polymerizablecyclic ether group in its molecule, a cationic polymerization initiator,a dye such as malachite green, tribromophenylsulfone, an optical colorcoupler such as leuco crystal violet, a thermal color developmentinhibitor, a plasticizer such as p-toluenesulfonamide, a pigment, afiller, an antifoaming agent, a flame retardant, a stabilizer, anadhesion imparting agent, a leveling agent, a stripping accelerator, anantioxidant, a perfume, an imaging agent or a thermal crosslinking agentin an amount of about 0.01 to 20 parts by weight based on 100 parts byweight of the total of the components (A) and (B) as required. These areused alone or in a combination of two or more.

[0070] The above photosensitive resin composition can be dissolved in asolvent such as methanol, ethanol, acetone, methyl ethyl ketone, methylcellosolve, ethyl cellosolve, toluene, N,N-dimethylformamide orpropylene glycol monomethyl ether or a mixed solvent thereof and appliedas a solution with a solid content of about 30 to 60% by weight asrequired.

[0071] Although the above photosensitive resin composition is notparticularly limited in terms of its form of use, it is preferred thatthe composition be used after applied on a surface of a metal such ascopper, a copper alloy, iron or an iron alloy as a liquid resist, dried,and then coated with a protective film as required or be used in theform of a photosensitive element.

[0072] Further, the thickness of the photosensitive resin compositionlayer, though varying depending on applications, is preferably about 1to 100 μm after drying. When the liquid resist is covered with theprotective film and used, a polymer film such as a polyethylene or apolypropylene is used as the protective film, for example.

[0073] The above photosensitive element can be obtained by, for example,coating the photosensitive resin composition on a polymer film such as apolyethylene terephthalate, a polypropylene, a polyethylene or apolyester as a substrate and then drying the coated composition. Theabove coating can be carried out by a known method such as a rollercoater, a comma coater, a gravure coater, an air-knife coater, a diecoater or a bar coater. Further, the drying can be carried out at 70 to150° C. for about 5 to 30 minutes. In addition, the amount of organicsolvent remaining in the photosensitive resin composition layer ispreferably 2% or less by weight in view of prevention of diffusion ofthe organic solvent in a subsequent step.

[0074] The thicknesses of these polymer films each are preferably 1 to100 μm. One of these polymer films may be used as a substrate for thephotosensitive resin composition layer, and other polymer film may belaminated on both surfaces of the photosensitive resin composition layeras a film for protecting the photosensitive resin composition. Adhesionbetween the protective film and the photosensitive resin compositionlayer is preferably lower than that between the photosensitive resincomposition layer and the substrate, and a film with a low rate ofoccurrence of fish eyes is also preferred.

[0075] Further, in addition to the photosensitive resin compositionlayer, the substrate and the protective film, the above photosensitiveelement may also have an intermediate layer or protective layer such asa cushion layer, an adhesive layer, a light absorbing layer or a gasbarrier layer.

[0076] To store the above photosensitive element, for example, it iswound around a cylindrical core either as it is or after a protectivefilm is further laminated on the other surface of the photosensitiveresin composition layer. In this case, the photosensitive element ispreferably wound up so that the substrate is outermost. At edge faces ofthe thus rolled photosensitive element roll, edge face separators arepreferably disposed from the viewpoint of protection of the edge faces,and moisture-proof edge face separators are preferably disposed from theviewpoint of prevention of edge fusion. Further, as a packing method, itis preferable to pack the roll with a black sheet having low moisturepermeability. Illustrative examples of the above core include plasticssuch as a polyethylene resin, a polypropylene resin, a polystyreneresin, a polyvinyl chloride resin and an ABS resin (AcrylonitrileButadiene Styrene copolymer).

[0077] To minimize developing time, a method of increasing viscosity(flowability) of the photosensitive layer is available. However, anincrease in the flowability is liable to cause degradation in storagestability. Further, when flowability is excessively low, followabilityto the substrate is liable to deteriorate.

[0078] The flowability is preferably 120 to 300 μm, more preferably 120to 260 μm, particularly preferably 140 to 220 μm. When the flowabilityis lower than 120 μm, the followability to the substrate is liable todeteriorate, while when the flowability is higher than 300 μm, thestorage stability is liable to deteriorate.

[0079] A method of evaluating the flowability is as follows. Firstly,the photosensitive layer is stripped from the substrate film, stuck to athickness of 2 mm without trapping bubbles, wrinkles, foreign matter andthe like therein, and punched by means of a 20-mm-φ dumbbell-shapedpuncher to prepare a test piece. Then, after the test piece is left tostand for 10 minutes on a test stand of a plastometer which has beenleft to stand in a thermostatic chamber at 30° C., a load of 5 kg isimposed on the test piece. An amount of change in thickness of the testpiece after 15 minutes is taken as the flowability. An example of theabove plastometer is an apparatus disclosed in Japanese PatentApplication Laid-Open No. 54255/1990.

[0080] To produce a resist pattern by use of the above photosensitiveelement having the above protective film, there can be used a method inwhich after removal of the protective film, the photosensitive resincomposition layer is pressed against or laminated on a substrate forforming a circuit at a pressure of about 0.1 to 1 MPa (about 1 to 10kgf/cm²) while being heated at about 70 to 130° C. The lamination isalso possible under a reduced pressure. A surface subjected to thelamination is generally a surface of a metal but is not particularlylimited.

[0081] The thus laminated photosensitive resin composition layer isirradiated with active light imagewise through a negative or positivemask pattern. As a light source of the above active light, a known lightsource which radiates an ultraviolet radiation, visible light or thelike effectively, such as a carbon arc lamp, a mercury vapor arc lamp, ahigh pressure mercury vapor lamp or a xenon lamp, is used.

[0082] After the exposure, a substrate on the photosensitive resincomposition layer, if present, is removed, and the photosensitive resincomposition layer is then developed by removing unexposed portionsthrough wet development, dry development or other development methodusing a developer such as an alkali aqueous solution, a water-baseddeveloper or an organic solvent. Thus, the resist pattern can beproduced.

[0083] Illustrative examples of the above alkali aqueous solutioninclude a dilute solution containing 0.1 to 5% by weight of sodiumcarbonate, a dilute solution containing 0.1 to 5% by weight of potassiumcarbonate, and a dilute solution containing 0.1 to 5% by weight ofsodium hydroxide. The pH of the above alkali aqueous solution ispreferably 9 to 11, and its temperature is adjusted according todevelopability of the photosensitive resin composition layer. Further,the alkali aqueous solution may contain a surfactant, an antifoamingagent, an organic solvent, and the like. As a method of carrying out theabove development, dipping, spraying, brushing, slapping or the like canbe used, for example.

[0084] To use the resist pattern after further curing, as apost-development treatment, the pattern may be subjected to heating atabout 60 to 250° C. or an exposure of about 0.2 to 10 J/cm² as required.

[0085] To etch the metal surface after the development, a cupricchloride solution, a ferric chloride solution, an alkali etchingsolution or the like can be used, for example.

[0086] To produce a printed wiring board by use of the, photosensitiveelement of the present invention, a surface of a substrate for forming acircuit is treated by a known method such as etching or plating with thedeveloped resist pattern used as a mask.

[0087] The above plating method may be copper plating, solder plating,nickel plating, gold plating or the like.

[0088] Then, the resist pattern can be removed by use of an aqueoussolution which is more alkaline than the alkali aqueous solution usedfor the development, for example.

[0089] As the above strong alkali aqueous solution, an aqueous solutioncontaining 1 to 10% by weight of sodium hydroxide or an aqueous solutioncontaining 1 to 10% by weight of potassium hydroxide can be used, forexample. As a method for carrying out the above removal, immersion,spraying or the like can be used. Further, the printed wiring patternhaving the resist pattern formed thereon may be a multilayer printedwiring board and may have small-diameter through holes.

[0090] A method for measuring time for removing a layer of thephotosensitive resin composition in the present invention can be carriedout by the following steps (1) to, (6), for example.

[0091] (1) The photosensitive resin composition is applied onto theforegoing substrate so that a layer of the photosensitive resincomposition may have a thickness of 37 to 42 μm, dried, and thenlaminated with a protective film as required, thereby obtaining aphotosensitive element. The surface of the above substrate is preferablya polyethylene terephthalate film not subjected to a special treatment,which makes it difficult to remove the photosensitive resin compositionlayer.

[0092] (2) A piece having a size of 30 mm×30 mm is cut out of thephotosensitive element obtained in (1) and used as a sample formeasuring the removal time.

[0093] (3) A surface of the substrate in the sample obtained in (2)which is opposite to the surface of the substrate on which thephotosensitive resin composition layer is present and a glass substrateare bonded together by use of a double-faced tape, and the existingprotective film is stripped as required so as to obtain a laminatehaving the glass substrate, the substrate and the photosensitive resincomposition laminated in this order.

[0094] (4) A spray nozzle (product of Spraying Systems Co., Japan, ahorn-shaped full corn type spray nozzle) having an internal diameter of1.2 mm is disposed so that a distance between a point of the spraynozzle (i.e., tip of the spray nozzle) which is closest to thephotosensitive resin composition layer and the photosensitive resincomposition layer may be 50 mm.

[0095] (5) A 10 wt % sodium carbonate aqueous solution is sprayed at aspray pressure of 0.05 MPa so as to fully cover the whole surface havinga size of 30 mm×30 mm of the photosensitive resin composition layer. Thespray pressure can be easily determined by measuring a pressure in atube through which the 1.0 wt % sodium carbonate aqueous solution issupplied to the spray nozzle.

[0096] (6) Then, the laminate is rinsed lightly in water in a water tankfor about 5 seconds, and the remaining photosensitive resin compositionlayer is observed. Time required to remove the photosensitive resincomposition layer completely by spraying is taken as the removal time.

[0097] A method for counting the number of holes where a cured film isbroken in the present invention can be carried out by, for example, thefollowing steps (1) to (8).

[0098] (1) The photosensitive resin composition is applied onto theforegoing substrate so that a layer of the photosensitive resincomposition may have a thickness of 37 to 42 μm, dried, and thenlaminated with a protective film as required, thereby obtaining aphotosensitive element. The surface of the above substrate is preferablya polyethylene terephthalate film not subjected to a special treatmentwhich makes it difficult to remove the photosensitive resin compositionlayer.

[0099] (2) On a copper-clad laminate (manufactured by Ein Co, Ltd.)having a 35-μm-thick copper foil laminated on both surfaces and having athickness of 1.6 mm, 18 three-continuous holes in which 3 holes eachhaving a diameter of 6 mm are continuously integrated and which has alength of 16 mm are formed by means of a puncher as shown in FIG. 1.Then, burrs produced at the time of forming the holes in the copper-cladlaminate are removed by use of a grinding machine (manufactured bySANKEI Co., Ltd.) having a brush corresponding to #600, and theresulting laminate is used as a substrate for counting the number ofholes where the cured film is broken. The holes are preferably formed ata fixed interval of about 6 to 18 mm.

[0100] (3) The photosensitive resin composition layer of thephotosensitive element obtained in (1) is laminated on one surface ofthe substrate obtained in (2) at a pressure of 0.4 MPa and a speed of1.5 m/min by use of a heat roller at 120° C., with the existingprotective film being stripped as required.

[0101] (4) The photosensitive resin composition layer laminated on thesubstrate in (3)is photo-cured with an exposure capable of photo-curing24 steps in a 41-step tablet (product of Fuji Photo Film Co., Ltd.,trade name: HITACHI 41 STEP TABLET) by means of an exposing device(product of ORC MANUFACTURING CO., LTD., trade name: HMW-201B ) having ahigh pressure mercury lamp so as to obtain a cured film, and then thesubstrate is stripped.

[0102] (5) A spray nozzle (product of Spraying Systems co., Japan, ahorn-shaped full corn type spray nozzle) having an internal diameter of1.2 mm is disposed so that a distance between a point of the spraynozzle (i.e., tip of the spray nozzle) which is closest to the curedfilm and the cured film may be 50 mm.

[0103] (6) A 1.0 wt % sodium carbonate aqueous solution is sprayedagainst the whole surface of the cured film at a spray pressure of 0.05MPa three times for 36 seconds in such a manner that the solution fullycovers the whole surface of the cured film. The spray pressure can beeasily determined by measuring a pressure in a tube through which the1.0 wt % sodium carbonate aqueous solution is supplied to the spraynozzle. Further, it is preferable to use a plurality of spray nozzles orswinging nozzles so as to spray the 1.0 wt % sodium carbonate aqueoussolution against the 18 three-continuous holes sufficiently.

[0104] (7) Then, the holes were observed so as to count the number ofholes where the cured film is broken.

[0105] (8) The above steps (1) to (7) are repeated for a total of 3times, and an average of the numbers of holes where the cured film isbroken is taken as the number of holes where the cured film is broken.

[0106] To measure time for removing the photosensitive resin compositionlayer of the photosensitive element when its thickness is not 37 to 42μm or to count the number of holes where a cured film obtained by curingthem is broken, there can be used, for example, a method in which aplurality of the photosensitive elements are laminated so that thephotosensitive resin composition layers may overlap each other and amethod comprising dissolving the photosensitive resin composition in asolvent such as acetone or dimethylformamide and preparing aphotosensitive element having a thickness of 37 to 42 μm so as to haveflowability of the above range. The latter method is preferred.

EXPERIMENTAL EXAMPLES

[0107] Hereinafter, the present invention will be described withreference to experimental examples.

Examples 1 to 8

[0108] Materials shown in Table 1 were mixed together so as to obtainsolutions Then, in the obtained solutions. Components (B) shown inTables 2 and 3 were dissolved so as to obtain solutions ofphotosensitive resin compositions. TABLE 1 Formulation (g) Materials (1)(2) Component Methacrylic Acid/Methyl Methacrylate/EthylActrylate/Styrene 89 89 (A) Copolymer (20/57/21/2 (Weight Ratio)),Weight Average (Solid (Solid Molecular Weight = 60,000, 60 wt % MethylCellosolve/Toluene = Content: Content: 6/4 (Weight Ratio) Solution,Dispersion = 2.5 53) 53) Methacrylic Acid/Methyl Methacrylate/ButylAcrylate/Butyl 19 19 Methacrylate Copolymer (24/44/15/17 (WeightRatio)), Weight (Solid (Solid Average Molecular Weight = 30,000, 60 wt %Methyl Content: Content: Cellosolve/Toluene = 6/4 (Weight Ratio)Solution, Dispersion = 11) 11) 2.0 Component 1,7-bis(9-acrydinylheptane)0.4 0 (C) N,N′,-tetraethyl-4,4′-diaminobenzophenone 0.04 0.132-(o-chlorophenyl)-4,5-diphenylimidazole Dimer 0 2.5 N-phenylglycine 00.05 Additives Leuco Crystal Violet 0.9 0.9 Tribromomethyl Phenylsulfone1.3 1.3 Malachite Green 0.05 0.05 Solvents Acetone 12.0 12.0 Toluene 5.05.0 Dimethylformamide 0 3.0 Methanol 3.0 3.0

[0109] TABLE 2 Material Component (B) Formulation Ex. 1 Ex. 2 Ex. 3 Ex.4 FA-024M (1) 36 — — — (2) — — — 36 FA-023M (1) — 36 — — HEMA-9P (1) — —36 — UA-13 (1) — — — — APG-400 (1) — — — — (2) — — — — 4G (1) — — — —

[0110] TABLE 3 Material Component (B) Formulation Ex. 5 Ex. 6 Ex. 7 Ex.8 FA-024M (1) — — — — (2) — — — — FA-023M (1) — — — — HEMA-9P (1) — — —— UA-13 (1) 36 — — — APG-400 (1) — 36 — — (2) — — 36 — 4G (1) — — — 36

[0111] The materials used in Tables 2 and 3 are shown below.

[0112] FA-024M: A compound (product of Hitachi Chemical Co., Ltd)represented by the above general formula (IV) wherein R is a methylgroup and m³, n² and n³ are 6 (average value), with a molecular weightof 1,282 and 18 alkylene glycol units each having 2 to 6 carbon atoms.

[0113] FA-023M: A compound (product of Hitachi Chemical Co., Ltd.)represented by the above general formula (III) wherein R is a methylgroup, m¹ and m² are −2 (average value), and n¹ is 12 (average value),with a molecular weight of 1.194 and 16 alkylene glycol units eachhaving 2 to 6 carbon atoms.

[0114] HEMA-9P: A compound (product of Shin-Nakamura ChemicalCorporation) represented by the above general formula (V) wherein R is ahydrogen atom, m⁴ is 1 (average value), and n⁴ is 9 (average value),with a molecular weight of 676 and 10 alkylene glycol units each having2 to 6 carbon atoms.

[0115] UA-13: Poly(ethylenepropylene glycol)modified urethanedimethacrylate (product of Shin-Nakamura Chemical Co., Ltd.), with amolecular weight of 1,056 and 20 alkylene glycol units each having 2 to6 carbon atoms.

[0116] APG-400: Heptapropylene glycol diacrylate (product ofShin-Nakamura Chemical. Co., Ltd.), with a molecular weight of 532 and 7alkylene glycol units each having 2 to 6 carbon atoms.

[0117] 4G: Tetraethylene glycol dimethacrylate (product of Shin-NakamuraChemical Co., Ltd.), with a molecular weight of 330 and 4 alkyleneglycol units each having 2 To 6 carbon atoms.

[0118] Then, the obtained photosensitive resin composition solution wasuniformly applied onto a polyethylene terephthalate film (product ofTeijin Ltd., trade name: G2-16) having a thickness of 16 μm, dried in ahot air convention type dryer at 100° C. for 10 minutes, and thenprotected with a polyethylene protective film, (product of TAMAPOLY Co,LTD., trade name: NF-13) so as to obtain a photosensitive element. Thephotosensitive resin composition layer had a thickness of 40 μm afterdrying, and its flowability was adjusted within 140 to 220 μm.

[0119] Then, a copper surface of a copper-clad laminate (HitachiChemical Co., Ltd., trade name: MCL-E-61) which was a glass epoxymaterial having a copper foil (having a thickness of 35 μm) laminated onboth surfaces was ground by use of a grinding machine (manufactured bySANKEI Co., Ltd.) having a brush corresponding to #600, rinsed withwater, and then dried by airflow. Then, the resulting copper-cladlaminate was heated to 80° C., and the above photosensitive resincomposition layer was laminated on the copper surface by use of a heatroller at 120° C. at a speed of 1.5 m/min with the protective film beingstripped.

[0120] Further, to evaluate resolution, a photo tool having Stopher's 21step tablet and a photo tool having a wiring pattern whose linewidth/space width were 30/30 to 200/200 (unit: μm) as a negative forevaluating resolution were closely laminated, and exposure was performedwith an amount of energy with which the number of steps remaining in theStopher's 21 step tablet after development would be 8.0. The exposurewas performed by use of an exposing device (product of ORC MANUFACTURINGCO., LTD., trade name: HMW-201B) having a high pressure mercury lamp.The resolution was evaluated based on the smallest value of a spacewidth between line widths when unexposed portions could be clearlyremoved by the development treatment. The smaller the value is, thebetter the resolution is evaluated as being.

[0121] To evaluate overhang stripping property, after laminated, exposedwith the predetermined exposure, and then developed with the abovedeveloper as described above, the laminate was immersed in a degreasingbath (containing 20 wt % of PC-455 (product of Meltex Inc.)) for 2minutes and then rinsed with water. Then, the resulting laminate wasimmersed in a soft etching bath (containing 150 g/l of ammoniumpersulfate) and then rinsed with water. Then, the laminate was immersedin a 10 wt % sulfuric acid bath for one minute to carry outpre-treatment, and then the resulting laminate was immersed in a coppersulfate plating bath (containing 75 g/l of copper sulfate, 190 g/l ofsulfuric acid, 50 ppm of chlorine ions and 5 ml/l of Copper Gleam PCM(product of Meltex Inc)) so as to plate the laminate with copper sulfateat room temperature and 1.2 A/dm² for 60 minutes. Subsequently, afterrinsed with water, the laminate was immersed in 10 wt % fluoroboric acidfor one minute and then immersed in a solder plating bath (containing 64ml/l of 45 wt % stannous fluoroborate, 22 ml/l of 45 wt % leadfluoroborate, 200 ml/l of 42 wt % fluoroboric acid, 20 g/l of PLUTIN LAconductivity salt (product of Meltex Inc.), and 41 ml/l of PLUTIN LAstarter (product of Meltex Inc.)) so as to solder-plate the laminate atroom temperature and 2 A/dm² for 15 minutes. After the resultinglaminate was rinsed with water and dried, the resist was stripped, andthe smallest plated line width where the resist residue was measuredunder an optical microscope, a projector and the like. The overhangstripping property was evaluated based on the value. The larger thevalue is, the better the overhang stripping property is.

[0122] Further, to evaluate tent reliability, a photosensitive resincomposition laminate was laminated on both surfaces of a substrate (SeeFIG. 1) which was a 1.6-mm-thick copper-clad laminate having irregularlyshaped holes each of which was the integration of three same-sized holeseach having a diameter of 4 mm, 5 mm or 6 mm, the resulting substratewas exposed at a predetermined exposure, and 36-second development wascarried out for three times. After the development, the number of holeswhere the laminate was broken among the 216 irregularly shaped holesshown in FIG. 1 were counted, evaluated as an irregularly shaped tentbreakage rate (the following expression (1)), and taken as the tentreliability.

Irregularly Shaped Tent Breakage Rate (%) (number of holes wherelaminate was broken/216)×100   (1)

[0123] Further, to evaluate removability of development sludge, a pieceof 0.4 m² was extracted from the photosensitive resin composition layerin the obtained photosensitive element,put in a 1.0 wt % sodiumcarbonate aqueous solution, agitated at30° C. for 90 minutes by use ofan agitator, and then left to stand for one week. After one week, sludgedeposited at the bottom of a vessel was agitated again and removed, andan amount of sludge remaining and deposited at the bottom was observed.An amount of removed sludge was evaluated based on the followingexpression (2).

[0124] ◯: 81% or more of sludge was removed.

[0125] Δ: 20 to 80% of sludge was removed.

[0126] X: 19% or less of sludge was removed.

Amount of Removed Sludge={(area of site where sludge remained and wasdeposited)/(area of bottom)}×100

[0127] The results of these are shown in Tables 4 and 5. TABLE 4 Ex. 1Ex. 2 Ex. 3 Ex. 4 Overhang Allowance (μm) 15 15 15 15 Irregularly ShapedTent 11 11 11 11 Breakage Rate (%) Resolution (μm) 45 45 45 50 SludgeRemovability ∘ ∘ ∘ x

[0128] TABLE 5 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Overhang Allowance (μm) 13 11 11 8 Irregularly Shaped Tent 22 50 50 89 Breakage Rate (%) Resolution (μm)50 45 50 45 Sludge Removability ∘ Δ x Δ

[0129] As is obvious from Tables 4 and 5, Examples 1, 2 and 3 inparticular are excellent in overhang removability and an irregularlyshaped tent breakage rate and also has good resolution and sludgeremovability.

Example 9

[0130] A methacrylic acid/methyl methacrylate/ethyl acrylate/styrenecopolymer (20/57/21/2(weight ratio)), a weight average molecular weight60,000, 105 g of 60 wt % methyl cellosolve/toluene=6/4 (weight ratio)solution (solid content: 64 g), 36 g of FA-024M, 0.4 g of1,7-bis(9-acridinylheptane), 0.04 g ofN,N′-tetraethyl-4,4′-diaminobenzophenone, 0.9 g of leuco crystal violet,1.3 g of tribromomethyl phenylsulfone, 0.05 g of malachite green, 12.0 gof acetone, 5.0 g of toluene and 3.0 g of methanol were mixed togetherso as to obtain a solution.

[0131] Then, the obtained photosensitive resin composition solution wasuniformly applied onto a polyethylene terephthalate film (trade name:G2-16, product of Teijin Ltd.) having a thickness of 16 μm, dried in ahot air convention type dryer at 100° C. for 10 minutes, and thenprotected with a polyethylene protective film (trade name: NF-13,product of TAMAPOLY CO., LTD.) so as to obtain a photosensitive resincomposition laminate. The photosensitive resin composition layer had athickness of 40 μm after drying.

Example 10

[0132] A methacrylic acid/methyl methacrylate/ethyl acrylate copolymer(17.5/52.5/30 (weight ratio)), a weight average molecular weight 80,000,89 g of 60 wt % methyl cellosolve/toluene=6/4 (weight ratio) solution(solid content: 53 g), a methacrylic acid/methyl methacrylate/butylacrylate/butyl methacrylate copolymer (24/44/15/17), a weight averagemolecular weight=30,000, 19 g of 60 wt % methyl cellosolve/toluene=6/4(weight ratio) solution (solid content: 11 g), 36 g of FA-024M, 0.4 g of1,7-bis(9-acridinylheptane), 0.04 g ofN,N′-tetraethyl-4,4′-diaminobenzophenone, 0.9 g of leuco crystal violet;1.3 g of tribromomethyl phenylsulfone, 0.05 g of malachite green, 12.0 gof acetone, 5.0 g of toluene and 3.0 g of methanol were mixed togetherso as to obtain a solution.

[0133] Then, the obtained photosensitive resin composition solution wasuniformly applied onto a polyethylene terephthalate film (trade name:G2-16, product of Teijin Ltd.) having a thickness of 16 μm, dried in ahot air convention type dryer at 100° C. for 10 minutes, and thenprotected with a polyethylene protective film (trade name: NF-13,product of TAMAPOLY CO., LTD.) so as to obtain a photosensitive resincomposition laminate. The photosensitive resin composition layer had athickness of 40 μm after drying.

[0134] Then, pieces having a size of 30 mm×30 mm were cut out of thephotosensitive elements obtained in the Examples 1, 2, 6, 8, 9 and 10and then laminated on glass substrates so that the polyethyleneterephthalate films of the photosensitive elements might come in contactwith the glass substrates, and then the polyethylene protective filmswere stripped, thereby obtaining laminates each having the glasssubstrate, the polyethylene terephthalate film and the photosensitiveresin composition laminated in this order.

[0135] Then, a spray nozzle (product of Spraying System Japan Co., Ltd.,a horn-shaped full corn type spray nozzle) having an internal diameterof 1.2 mm was disposed so that a distance between a point of the spraynozzle (i.e., tip of the spray nozzle) which was closest to thephotosensitive resin composition layer and the photosensitive resincomposition layer might be 50 mm. A 1.0 wt % sodium carbonate aqueoussolution was sprayed at a spray pressure of 0.05 MPa so as to fullycover the whole surface having a size of 30 mm×30 mm of thephotosensitive resin composition layer. Time required to remove thephotosensitive resin composition completely was taken an removal time ofthe photosensitive resin composition layer. The results are shown inTable 6.

[0136] Further, on a 1.6-mm-thick copper-clad laminate (product of EinCo, Ltd.) having a 35-μm-thick copper foil laminated on both surfaces,18 three-continuous holes in which 3 holes each having a diameter of 6mm were continuously integrated and which had a length of 16 mm wereformed by means of a puncher as shown in FIG. 1. Then, burrs produced atthe time of forming the holes were removed by use of a grinding machine(product of SANKEI Co., Ltd.) having a brush corresponding to #600, andthe resulting laminate was used as a substrate for counting the numberof holes where the cured film was broken. The holes were formed atintervals of 10 mm.

[0137] Then, the photosensitive resin composition layers of thephotosensitive elements obtained in the obtained Examples 1, 2, 6, 8, 9and 10 were laminated at a pressure of 0.4 MPa and a speed of 1.5 m/minby use of a heat roller at 120° C., with the polyethylene protectivefilms being stripped. The photosensitive resin composition layerslaminated on the substrates for counting the number of holes where thecured film was broken were photo-cured with an exposure capable ofphoto-curing 24 steps in a 41-step tablet (product of Fuji Photo FilmCo., Ltd., trade name: HITACHI 41 STEP TABLET) by means of an exposingdevice (product of ORC MANUFACTURING CO., LTD., trade name: HMW-201B)having a high pressure mercury lamp so as to obtain cured films, andthen the substrates were stripped.

[0138] Then, a spray nozzle (product of Spraying System Japan Co., Ltd.,a horn-shaped full corn type spray nozzle) having an internal diameterof 1.2 mm was disposed so that a distance between a point of the spraynozzle (i.e., tip of the spray nozzle) which is closest to the curedfilm and the cured film might be 50 mm. A 1.0 wt % sodium carbonateaqueous solution was sprayed against the whole surface of the cured filmat a spray pressure of 0.05 MPa three times for 36 seconds in such amanner that the solution would fully cover the whole surface of thecured film The holes were observed so as to count the number of holeswhere the cured film was broken The results are shown in Table 6. Sixspray nozzles were disposed at intervals of 30 mm so that the 1.0 wt %aqueous sodium carbonate solution might be sufficiently sprayed againstthe 18 three-continuous holes. TABLE 6 Removal Time Number of HolesWhere (seconds) Cured Film was Broken Example 1 18 3 Example 2 18 3Example 6 18 6 Example 8 18 15  Example 9 22 3 Example 10 25 3

[0139] As described above, an improvement in production line of aprinted wiring board was attempted by use of the photosensitive elementsobtained in Examples 1, 2, 6, 8, 9 and 10. Of these, the photosensitiveelements obtained in Examples 1 and 2 in particular could prevent entryof an etching solution, a plating solution or the like into throughholes efficiently, prevent poor conduction, an improper short and thelike in a printed wiring board, and produce printed wiring boards athigh yields.

[0140] Possibility of Industrial Utilization

[0141] As described above, the present invention produces printed wiringboards at high yield, accelerates a production line of the printedwiring boards significantly and reduces production time of the printedwiring boards, thereby making it possible to improve workability andproductivity. Therefore, the present invention is useful.

[0142] Further, the present invention is also useful for achieving dhigher density and higher resolution of a printed wiring board.

1. A photosensitive resin composition which satisfies the following (1)and (2): (1) when a 1.0 wt % aqueous sodium carbonate solution issprayed by a spray on a layer of the photosensitive resin compositionhaving a thickness of 37 to 42 μm under the following conditions, thephotosensitive resin composition layer being able to be removed within20 seconds, the conditions being that an internal diameter of a nozzleof the spray is 1.2 mm, a spraying pressure is 0.05 MPa, and a distancebetween a point of the spray nozzle which is closest to thephotosensitive resin composition layer and the photosensitive resincomposition layer is 50 mm; and (2) when the 1.0 wt % aqueous sodiumcarbonate solution is sprayed three times for 36 seconds under the aboveconditions on a cured film obtained by laminating a layer of thephotosensitive resin composition having the above thickness on acopper-clad laminate having 18 three-continuous holes in which 3 holeseach having a diameter of 6 mm are continuously integrated and which hasa length of 16 mm, and then photo-curing the layer with an exposurecapable of curing 24 steps in a 41-step tablet. The number of holeswhere the cured film is broken being 5 or less.
 2. The composition ofclaim 1, wherein the photosensitive resin composition layer is removablewithin 19 seconds.
 3. The composition of claim 1, wherein thephotosensitive resin composition layer is removable within 18 seconds.4. A photosensitive resin composition comprising (A) a binder polymer,(B) a photopolymerizable compound and (C) a photopolymerizationinitiator, wherein the component (B) contains polyalkylene glycoldi(meth)acrylate having both an ethylene glycol chain and a propyleneglycol chain in its molecule, and the component (C) contains acridine oran acridine-based compound having at least one acridinyl group in itsmolecule.
 5. The composition of claim 4, wherein the component (C)contains an acridine-based compound having at least one acridinyl groupin its molecule and represented by a general formula (II):

(wherein R³ represents an alkylene group having 6 to 12 carbon atoms).6. A photosensitive resin composition comprising (A) a binder polymer,(B) a photopolymerizable compound and (C) a photopolymerizationinitiator, wherein the component (A) is a polymer component having aweight average molecular weight of 30,000 to 70,000, and the component(B) contains a photopolymerizable compound which has at least oneethylenically unsaturated bond in its molecule and which has 15 or morealkylene glycol units each having 2 to 6 carbon atoms.
 7. Aphotosensitive resin composition comprising (A) a binder polymer, (B) aphotopolymerizable compound and (C) a photopolymerization initiator,wherein the component (A) is a polymer component having a weight averagemolecular weight of 30,000 to 70,000, and the component (B) contains aphotopolymerizable compound which has at least one ethylenicallyunsaturated bond in its molecule and a molecular weight of not lowerthan
 900. 8. The composition of any of claims 4 to 7, wherein based on100 parts by weight of a total of the components (A) and (B), the amountof the component (A) is 40 to 80 parts by weight, the amount of thecomponent (B) is 20 to 60 parts by weight, and the amount of thecomponent (C) is 0.01 to 3 parts by weight.
 9. A photosensitive elementprepared by applying the photosensitive resin composition of any ofclaims 1 to 8 on a substrate, and drying the applied composition.
 10. Aproduction method of a resist pattern, comprising the steps of:laminating the photosensitive element of claim 9 on a substrate forforming a circuit so that the photosensitive resin composition layer maycome in intimate contact with the substrate: irradiating it with activelight imagewise so as to photo-cure an exposed potion; and removing anunexposed portion by development.
 11. A production method of a printedwiring board, comprising the step of: etching or plating a substrate toform a circuit which has a resist pattern produced thereon by the resistpattern production method of claim 10.